1. Field of the Invention
The present invention relates to a portable electronic device and particularly to a power control method for a portable electronic device.
2. Description of the Prior Art
One important function of portable electronic devices is to process and store data for users. For increasing the use time of a portable electronic device, if the portable electronic device is not used for a long period, it enters a sleep mode wherein most components of the portable electronic device, besides those needed to recover and a volatile memory to store information, are stopped. Similarly, to secure data, when power supply, such as a battery, is less than a predetermined amount, the portable electronic device enters sleep mode to decrease power requirements.
TABLE AConditionPercentage of total powerPower of other circuits in25%sleep modePower of SDRAM in sleep mode75%3.8 V DC-in in sleep mode100% 
Referring to Table A, some power is required in sleep mode. Important information, such as security settings, is stored in the volatile memory. Without power, the volatile memory cannot retain data. In sleep mode, power for retaining data constitutes the majority of the total power consumed of the portable electronic device and reaches 75%. The advantage of sleep mode is the short response time to return to work. In portable electronic devices not used for long periods, however, power consumed in quick recovery is not economical.
In current portable electronic devices, when remaining battery supply is 20%, the portable electronic device automatically enters sleep mode, retaining data in the volatile memory for at least 72 hours. data stored in the volatile memory is lost when the power is exhausted, thereby inconveniencing users.